The ex-Barcelona attacker was taken off with bone bruising to the knee against Lyon earlier this month and sat out his side's recent victories over Strasbourg and Metz.
Pochettino was originally confident about Messi's chances of making the cut for Tuesday, and the PSG boss has all but confirmed that the 34-year-old will be available for his reunion with Pep Guardiola.
Speaking to the media ahead of the clash, Pochettino said: "He is in a very good way. I think he will be in the squad but I still haven't decided on the starting XI."
Messi made his Champions League debut for PSG in a 1-1 draw with Club Brugge two weeks ago, and the Argentine is still waiting for his first goal in navy blue.